PSXII-12 - Heritage Raramuri Criollo Cattle Production as a Potential Strategy for Conservation of Black Grama in the Chihuahuan Desert

Abstract: The Chihuahuan desert ecosystem has experienced a decrease in black grama (Bouteloua eriopoda), a perennial grass species with high ecological value, alongside a subsequent increase in mesquite (Prosopis glandulosa). This trend is thought to be due to several management- and environment-related factors. We compared diet selection of a heritage Raramuri Criollo (RC) vs. Angus-X-Hereford (AH) cattle, typical of the region, using fecal DNA metabarcoding conducted by a commercial laboratory to determine the proportion of black grama and mesquite in samples. RC and AH cows grazed two adjacent pastures (~1,100 ha) separately, switched at the mid-point of each period. Rectal fecal samples were collected from 10 cows/ breed/ pasture/ period. The study was replicated across seasons (growing and dormant) for three consecutive years (240 total fecal samples) in a completely randomized design. Relative abundance of plant species was ranked over the entire study and by season. The MIXED procedure of SAS 9.4 was used to analyze the proportions of black grama and mesquite in fecal samples by breed, season, year, and all interactions. Black grama was a more important forage resource than mesquite (ranked 8 vs. 11), particularly during dormancy (ranked 3 vs. 7). When examined by breed, AH fecal samples had twice the percentage of black grama vs. RC (P< 0.05) and even more so during the dormant season (P< 0.05). In contrast, RC fecal samples tended to contain a greater percentage of mesquite (P=0.05). Adjustments for BW differences between breeds (545 vs. 350 kg mean BW for AH vs. RC respectively) suggest that AH consumed 3.09-fold more black grama while RC consumed 1.59 times more mesquite. Differences in diet composition appear to support the hypothesis that RC cattle could impose a lighter grazing pressure on black grama populations, potentially serving as a conservation management tool on Chihuahuan Desert rangelands.